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LF104: Molecules, Cells And Organisms > 22 - Membranes and Lipids > Flashcards

22 - Membranes and Lipids Flashcards

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1
Q

membrane general functions

A
  • semipermeable barrier
  • detects and interprets changes on extracellular environment
  • provides anchorage sites for extracellular proteins and cytoskeleton
  • provides an alternative environment to the cytoplasm
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2
Q

Compartmentalisation in eukaryotic cells

A

Eukaryotic cells are compartmentalised

Compartments are enclosed in membranes

Membrane proteins important for functions

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3
Q

Membrane model structure name

A

fluid mosaic model

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4
Q

what largely defines the function of a protein

A

largely defined by the protein molecules, lipids, and complexes that reside in it

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5
Q

Membrane topology - diagram

A
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6
Q

how many lipids in lipid bilayers

A

~5 x 10^6 lipid molecules per micrometre squared of bilayer
- plasma membrane of a typical cell contains ~10^9 lipids

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7
Q

different types of lipids found in membranes

A

Phospholipids
Glycolipids
Cholesterol

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8
Q

different molecules found in membranes
- how different membranes differ in their composition

A
  • proteins, lipids and carbohydrates found in membranes
  • composition of these molecules depends on membrane function and structure
  • e.g. mitochondria contain large majority of protein in membrane buildup, for electron transport chain, ATP synthase, etc.
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9
Q

Key biological functions of lipids

A
  • fuel for metabolism
  • membranes:
  • phospholipids - phosphoglycerides and sphingolipids
  • glycolipids
  • cholesterol
  • signalling molecules
  • steroid hormones, e.g. sex hormones and cortisol
  • eicosanoids: short range signalling molecules involved in pain, inflammation, etc.

Vitamins: A, D, E and K

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10
Q

general characteristics of lipids

A
  • lipids very diverse in structure
  • defined by hydrophobocity rather than structure
  • not soluble in water
  • soluble in organic solvents, e.g. chloroform, ethanol, due to polarity of these substances
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11
Q

glycerol derivatives and their functions
- what bonds they contain

A

triacyl glyceride - storage of fuel for metabolism
- contain ester bonds

  • phosphoglycerides - key component of biological membranes
  • contain ester bonds
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12
Q

Phospholipids - amphipathic

A
  • polar phosphate head is hydrophilic
  • fatty acid chain are hydrophobic
  • amphipathic - both preoperties in same molecule
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13
Q

hydrophobic parts of membranes

A
  • they exclude water
  • are extensive
  • close in on themselves - no edges for contact with water - natural shape
  • self-sealing
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14
Q

structure/properties of fatty acids

A
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15
Q

saturated fatty acids
- three systems for numbering carbons

A
  • no C=C double bonds
    different carbon numbering system:
  • 1, 2, 3 - chemical numbering system
  • a, B, y - biochemical still used in metabolism
  • w, w-1, w-2 - used in nutrition
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16
Q

what affects melting point of fatty acids

A
  • melting point increases with increasing chain length
  • MP decreases with increasing double bonds - more fluid
17
Q

Unsaturated fatty acids
- effect on melting point

A
  • contain C=C double bonds
  • double bonds in fatty acids are usually cis

DIfference between cis and trans
- trans - almost straight
- cis - introduces a kink in the chain

  • MP decreases with increasing double bonds - more fluidity
18
Q

irregulat packing of fatty acids tails info

A
  • C=C cis double bond introduces kink in the chain
  • causes irregular packing of fatty acid chain
  • leads to lower MP or more fluidity
19
Q

What are essential fatty acids - functions

A

must be obtained in diet
- as have important function in cell membrane, signalling

  • starting point for making arachidonic acid
20
Q

Arachidonic acid info and function

A
  • synthesised from linoleic acic
  • precursor for eicosanoids (polyunsaturated fatty acids, present in neural function)
  • important function as part of phospholipids in membrane
  • plays important role in inflammation
  • conditionally essential in diet
  • Structure discovered by Ida Smedley-Maclean
21
Q

Eicosanoids function
- process behind it

A
  • important in pain and inflammation

Process:
- inflammatiry signal sent to membranes
- causes release of arachidonic acid
- followed by:
- release of other eicosanoids or release of prostaglandin (aspirin or ibuprofen needed)

22
Q

Prostagladin info function

A
  • lipids made at sites of injury or tissue damage
  • control processes in dealing with injury and tissue damage
  • e.g. inflammation, blood flow, blood clots etc.
23
Q

How can phospholipids be modified

A
  • phosphate groups can be modified
  • different grous can be added/bonded to the phosphate head, e.g. hydroxyl, amine, etc.
24
Q

Biological function of head groups in phospholipids

A

Phosphatidylcholine and phosphatidylinositol can be cleaved
- inositol and choline are important signalling molecules in some metabolic pathways
- they can both transmit signals into cells, etc.

25
Q

two key phospholipids and uses

A
  • phosphoglycerides -
  • sphingolipids - based on sphingosine amino acids
  • used in sphingomyelin, to make schwann cells and myelin sheaths
  • increases speed of electrical impulse and neurone transmission
  • sphingomyelin also used in signal trransduction and apoptosis
26
Q

glycolipids info

A
  • sugar containing lipids
  • sugar instead of phosphate group
  • can be more than one sugar unit
  • in animal cells, ddrived from sphingosine, not glycerol
  • sugar always on outside of the cell

Functions: immune response, cell recognition and attachment (signalling)

27
Q

cholesterol in membrane general info

A

sterol - modified steroid
- steroids have common structure of four hydrocarbon rings
- is the only steroid in membranes (only in animals)
- has important effects on membrane fluidity

LF104: Molecules, Cells And Organisms (25 decks)

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